The present invention relates generally to yarns, fabric and safety apparel formed therefrom, and more particularly to fabric and apparel that meets nationally-recognized standards for flame-resistance, high-visibility, and electric arc resistance.
Authorities worldwide have recognized the need to protect occupational workers from the inherent hazards of apparel that is deficient in contrast and visibility when worn by workers exposed to the hazards of low visibility. These hazards are further intensified by the often complex backgrounds found in many occupations such as traffic control, construction, equipment operation, and roadway maintenance. Of major concern is ensuring that these workers are recognized by motor vehicle drivers in sufficient time for the drivers to slow-down or take other preventive action to avoid hazard or injury to the workers. Thus, worker safety is jeopardized when clothing not designed to provide visual identification is worn by persons working in such dangerous environments. While there are no federal regulations governing the design, performance, or use of high-visibility apparel, local jurisdictions and private entities have undertaken to equip their employees with highly luminescent vests. One national standards organization, known as the American National Standards Institute (ANSI), in conjunction with the Safety Equipment Association (ISEA), has developed a standard and guidelines for high-visibility luminescent safety apparel based on classes of apparel.
Similarly, and in related fashion, certain of the above-mentioned occupations also require safety apparel that is flame resistant or electric arc resistant. For example, electric utility workers who may be exposed to flammable situations or to momentary electrical arc require apparel that is flame and/or arc resistant. In the United States, there is a nationally-recognized standard providing a performance specification for flame resistant textile materials for safety apparel, referred to as the American Society for Testing and Materials (ASTM), standard F 1506. This standard provides performance properties for textile materials used in apparel that represent minimum requirements for worker protection. One component of this standard is the vertical flame test which measures whether an apparel will melt or drip when subjected to a flame, or continue to burn after the flame is removed. A second component of flame resistance is arc thermal performance which is tested in accordance with ASTM standard F 1959 to meet acceptance criteria found in National Fire Prevention Association (NFPA) Standard 70E.
Until recently, various items of safety apparel were produced to meet one or the other of these nationally-recognized standards, but none were known in the art that were capable of meeting all of the standards for flame-resistance, electric arc resistance, and high-visibility. There are now known, however, fabric and apparel formed therefrom that will meet the minimum requirements for high-visibility and that will meet the vertical flame test for flame-resistance. As of the date of this invention, however, no fabric or apparel has heretofore been developed that will satisfy the above standards for high-visibility and flame-resistance, as well as arc thermal performance.
The present invention is directed to a yarn, fabric, and apparel formed therefrom, that meets the minimum guidelines laid out in ANSI/ISEA-107-1999, xe2x80x9cAmerican National Standard for High-Visibility Safety Apparelxe2x80x9d, the vertical flame test of ASTM F 1506, xe2x80x9cStandard Performance Specification for Flame Resistant Textile Materials for Wearing Apparel for Use by Electrical Workers Exposed to Momentary Electric Arc and Related Thermal Hazardsxe2x80x9d, and the electric arc thermal performance criteria of NFPA 70E, xe2x80x9cElectrical Safety Requirements for Employee Workplacesxe2x80x9d when tested in accordance with ASTM F 1959, xe2x80x9cStandard Test Method for Determining the Arc Thermal Performance Value of Materials for Clothingxe2x80x9d.
ANSI/ISEA-107-1999 specifies requirements for apparel capable of signaling the wearer""s presence visually and intended to provide conspicuity of the wearer in hazardous situations under any light conditions by day, and under illumination by vehicle headlights in darkness. As used herein, and as defined in ANSI/ISEA-107, xe2x80x9cconspicuityxe2x80x9d refers to the characteristics of an object which determine the likelihood that it will come to the attention of an observer, especially in a complex environment which has competing foreground and background objects. Conspicuity is enhanced by high contrast between the clothing and the background against which it is seen. The ANSI standard specifies performance requirements for color, luminance, and reflective area. Three different colors for background and combined performance are defined in the standard. The color selected should provide the maximum contrast with the anticipated background for use of the apparel. Several combinations are described in the standard depending upon the intended use. For example, the ANSI standard describes three classes of conspicuity. For utility workers, the apparel would meet either Class 2 or Class 3 (Appendix B of ANSI 107-1999).
ASTM F 1506 provides a performance specification that may be used to evaluate the properties of fabrics or materials in response to heat and flame under controlled laboratory conditions. For exposure to an open flame, a fabric or apparel must not melt, drip, or continue to burn after the flame is removed. The properties of material for basic protection level wearing apparel should conform to the minimum requirements for woven or knitted fabrics with respect to breaking load, tear resistance, seam slippage, colorfastness, flammability before and after laundering, and arc testing. ASTM F 1506 specifies these performance characteristics based on fabric weight ranges, expressed in ounces per square yard. ASTM F 1506 establishes that an afterflame may not persist for more than 5 seconds when subjected to the arc testing of ASTM F 1959, discussed below.
ASTM F 1959 provides a test method for measuring the arc thermal performance value of materials intended for use as flame resistant clothing for workers exposed to electric arcs of the magnitude that would generate heat flux rates from between 2 and 600 cal/cm2s. The arc thermal performance value (ATPV) is the incident energy on a fabric or material that results in sufficient heat transfer through the fabric or material to cause the onset of second-degree bums. Incident energy is the total heat energy received at a surface as a direct result of an electric arc. As will be understood by those skilled in the art, the higher the ATPV, the more protective the apparel.
NFPA 70E establishes arc thermal performance acceptance criteria for occupational employee apparel. For outer garments, the minimum acceptable arc thermal performance value is 5.0 cal/cm2.
The rigorous performance specifications of each of the above standards are met by the fabric and safety apparel formed from the unique yarns of the present invention. It has been found that a yarn formed substantially from modacrylic and certain xe2x80x9chigh performance, high energy absorptivexe2x80x9d aramid fibers will yield a fabric and apparel that meet all of the above standards. As used herein, the term xe2x80x9cfiberxe2x80x9d includes staples and filaments.
Modacrylics have characteristics that solve two of the problems addressed by the present invention. First, modacrylic yarns are inherently flame resistant, with the level of flame resistance varying based upon the weight percentage of acrylonitriles in the composition. Secondly, modacrylic yarns are very receptive to cationic dyes, which are known for their brilliance.
Aramid fibers are manufactured fibers in which the fiber-forming material is a long chain synthetic polyamide having at least 85% of its amide linkages (xe2x80x94NHxe2x80x94COxe2x80x94) attached directly to two aromatic rings. Poly-para-phenylene terephthalamide is one such aramid which is produced from long molecular chains that are highly oriented with strong interactive bonding. Yarns that include at least about 3 percent of these materials solve the third problem (arc thermal performance) addressed by the present invention. That is, when blended with the modacrylic fibers, the high tensile strength and high energy absorption properties of these materials contribute to high values for thermal performance and resistance to break open (formation of holes) when subjected to an electric arc. As used herein, and as well known in the art, the term xe2x80x9caramidxe2x80x9d includes xe2x80x9cmeta-aramidsxe2x80x9d such as Nomex(copyright) and Conex(trademark), and xe2x80x9cpara-aramidsxe2x80x9d such as Kevlar(copyright) and Technora(copyright).
In an exemplary embodiment, fabric constructed according to the present invention is formed from yarns that are a blend of modacrylic fibers and poly-paraphenylene terephthalamide fibers that are spun in accordance with conventionally known techniques. It has been found that fabrics formed from such blended yarns, wherein the modacrylic fibers used to form the yarns provide a flame-resistance rating that meets at least the vertical flame burn test minimum criteria for safety apparel. The blended poly-paraphenylene terephthalamide fibers provide strength and energy absorption to meet at least the minimum ATPV for safety apparel. The fabric may be either woven or knit. The inherently flame resistant material is dyed in conventional fashion in a jet dye machine with cationic, or basic, dyestuff compositions to obtain International Yellow or International Orange hues that will meet the luminescence and chromacity requirements of ANSI/ISEA-107-1999.
While the exemplary embodiment described herein is formed from an intimate blend of modacrylic and high performance, high energy absorptive fibers, the yarn may be formed from modacrylic filaments and high performance, high energy absorptive filaments in a uniform distribution to form each yarn end.
These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of the preferred embodiment.